Characteristics of Stars

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2 Definition of a starIt’s a body of gases that gives off lots of energy in the form of light and heatThey vary in size and mass, some are smaller that 20 km in diameter or up to a 1000 times the size of our sun!

3 Variations in composition and temperatureUsing a spectrometer, scientists can determine what type of gases compose a starEvery chemical element has a characteristic spectrum

9 Actual Motion of StarsThey rotate on an axis, they revolve around other stars, and they move towards or away from earthDon’t forget the red shift

10 Distance to the StarsIt’s measured in light years- the distance that light travels in one year ( about 9.5 trillion km)Light from the sun takes about 8 minutes to reach earth

11 ParallaxScientists can use this to measures stars within 1000 light years of accuracy by measuring the angle between a stars’ apparent position over a period of 6 monthsThe closer the star, the larger the angle

12 Stellar MagnitudesThe visibility of a star depends on its brightness and distance from earthOver 3 billion stars can be seen through a telescope, but only 6000 can be seen with the naked eyeThe 2 scales that scientists use to measure brightness are apparent magnitude and absolute magnitude

13 Apparent Magnitude The brightness of a star as is appears from earthThe most powerful telescopes can detect stars with an apparent magnitude of about 29Those stars are 1.5 billion times fainter than those seem with a naked eye

15 Absolute MagnitudeHow bright a star would be if it were 32.6 light years awayScientists use this distance because it’s equal to one parsec

16 Classification of starsMain-sequence stars- stars that are visible in the night sky, this includes the sunSuper giants – are bright because they have so much surface area to project lightWhite dwarfs- these stars are hot and dim because of their size